Over the past several years, the automotive industry has seen a significant increase in the number of in-vehicle intelligent systems and services. These systems and services are intended to facilitate and improve communication between the user and the vehicle as well as the user and the outside world. For safety reasons, the industry is focused on providing hands-free features to people who use wireless communications in their vehicle. One area that needs improvement is the quality of the voice communication in the vehicle. Efforts to improve the quality of the voice communication has centered on introducing new audio signal processing algorithms, new distributed microphones, and new microphone arrays. To help shield transmitted audio signals from external interference, the industry has introduced an optical network according to a communication protocol known as the Media Oriented Systems Transport or MOST®. Further information about the MOST® optical network protocol may be found on the Internet at www.oasis.com.
Each of these developments has significantly increased the complexity of an audio hands-free communication system. Recently, there has been a need to de-centralize the audio signal processing systems in a vehicle and make units modular in order to improve their performance and reduce cost. This effort has introduced a virtual limit on the number of distributed microphones or microphone array units that can be simultaneously routed or be used by distributed signal processing systems. The primary reason for this limitation is based on the amount of independent audio channels that can be transported over the MOST® optical network communication protocol as well as the variety of sample rates simultaneously supported by these audio streams and rapidly growing system complexity.
Today, in the automotive environment, the MOST® optical network communication protocol has a limit of four independent audio streams (channels) that can be assigned to a control unit that transmits over the optical network. This is primarily due to limitations of current hardware interfaces. Current hardware interfaces sample at the same frequency rate supported by the MOST® optical network communication protocol which is 38 kHz, 44.1 kHz, and 48 kHz. Even though the original design of the MOST® optical network communication protocol supports up to 15 synchronous 4-byte wide audio channels, the interface configuration to the optical network restricts the number of synchronous audio channels that can be assigned to an in-vehicle module. To improve overall user experience and support better quality voice communications, a need exists for additional microphones and microphone arrays. Simply adding additional transducers in known systems, however, will result in a significant cost increase and system complexity.
Accordingly, further improvements are needed to facilitate the transmission of audio signals over current optical network communication protocols. There is also a need to reduce the number of control units in order to reduce cost. It is, therefore, desirable to provide an improved device and procedure for transmitting and distributing audio signals in a vehicle to overcome most, if not all, of the preceding problems.
While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.